Killer Sudoku: The Lethally Addictive Sudoku Variant

Sudoku for the brave of heart! Sharp-minded solvers willing to venture into dangerous puzzle territory will find satisfaction navigating these killer sudoku. Each one looks like a regular sudoku, but with a challenging twist: there are also additional boxes surrounding sets of squares. Those boxes contain tiny numbers that tell you the sum of the digits inside the box. It's a brain-stretching variation that will delight sudoku fans everywhere.